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The P0457 code can either be the gas cap being lose, or thrown in conjunction with the P0447 code, they typically come in a pair.
Lets Begin!;

the connecter that typically is the culprit for the P0447 code is shown in this picture on the right hand side of the charcoal canister (located at the passanger rear of the vehicle), usually it becomes dirty and/or corroded causing the CEL, take off this connector and inspect for corrosion and a possible poor connection, some of the time this is all that is required, if all looks well keep the connector un plugged and turn the car on, as the car is running use a volt meter and set it to 20 VDC (it's the setting mine had), if it reads 12v the issue is somewhere else, quickly check the rubber hoses going into the canister for damage as they are not protected from debris coming off the rear wheel, if it reads any less you have a break in the wire going to that plug. use a knife and cut the loom behind that connector and inspect the wiring, if all looks ok, remove the charcoal canister by taking off the 3-12mm bolts holding it in place, carefully lower it and not damage the rubber hosing going to the box. it's slightly smaller than a shoe box if you are still for some reason not sure what it looks like.

here you can see the canister lowered and move out of the way, the three wires that were hidden in the loom, as i peeled it back the wire fell apart from corrosion, chances are that was my issue, with the canister out of the way it's easy to split the look and access the wire, once you split it farther you'll notice the two wires (yellow/green) that are supposed to be connected together with solder, typical location for the break, trim the wires, tin the ends, and start with adding length to the connector itself.

here you can see me extending the wire with some 18g wiring, nothing special, solder the ends and use shrink tubing, simple stuff, red to the yellow/green, and black to the other one.

connector done and extended, shrink tubing used on both wires and a larger piece to help prevent moisture getting into the patch.

1) this is the fuel tank pressure solenoid clip, the p1400 CEL stems from this location, most of the time it's due to the break in the wiring, some of the time it's the solenoid above the center diff. that has failed, i suggest checking the connector/wiring first and foremost. you will also notice the yellow/green wire here also, remember the two Y/G wires that were soldered together going to the charcoal canister clip? yup. look at the two red dots, that is the same wire, since the corroded wire broke, it also resulted in the p1400 code, ironic huh!

2) This is the NEGETIVE wire going to the charcoal canister clip.

3) These are the POSITIVE wires going to the charcoal canister, strip and solder these together, then solder both (2) and (3) wires to the clip, matching colors obviously.

wires soldered and extended, connected to the clip before shrink tubing and 3x layers of electrical tape.

wiring sealed up and connector cleaned, use lots of electrical tape!, replace both connectors using dielectric grease to prevent corrosion, double check your work and replace charcoal canister with 3x 12mm bolts.

picture is same as before, replace everything to look the same, i tucked the wire for the clip up and over the rubber hosing to prevent any possible damage, extended it a little longer for this reason., double check your work, go inside the car and reset CELs with access port if you have one, if not, take the negetive terminal off of your battery, place aside and hold your foot on the brake pedal for 10secs. replace terminal, tighten and start the car, the car will re learn it's idle and if all went well, the CELs will be off.

TADA! no more CELs! saved $400+ from NOT going to the dealership!

Hope this helps, this relates to 2002-2007 WRX's, STi's, outbacks and i believe forresters, possibly older generations as well, if you need a hand i can help also! sorry for the spelling mistakes and this being rushed!

I am getting this code and this code only on an inconsistant basis. Neither of the other two. Could a faulty connector be the cause of just this one CEL without causing either of the other two?

Could be a bad gas cap..Unfortunately if you don't have a tester, you can only replace it and then let it see what happens. Because chances are if you don't have the cap tester, you won't have a leak machine. I picked one up at my dealer for like $14, so it might be worth a shot. And if it's something else..you have a new gas cap that is known to be good

I did get the new gas cap already and it worked for a few days, but then CEL came on again, same one and only code. I am testing a theory right now but I believe that the CEL is only coming on for me when my fuel tank level is about half or lower. Does that help anyone narrow down what it could be? I am going to just not let my car get below a half tank for the next 2-3 weeks and see if I can keep this CEL at bay. If it doesn't come on I will be pretty confident in relating it to fuel level. Engine load level, boost level, ambient temp and humidity, none of this seems to play into whether it comes on or not. I have intentionally subjected the vehicle to various load and climate conditions and the CEL hasn't come on above half tank. Below half tank, just cruising in 6th gear on the highway and boom CEL on and cruise flashing.

Great write up man. I have these codes too so i was gonna do this and when i pulled down the charcoal can down there was both of the female side of the plugs, but they weren't plugged into anything and there are no other wires hanging under there. Do you (or anyone) know where these other wires would be? Like what would their routing be so i can dig around and see if they are just removed or what.

I had the p0447 code evap emission control system vent circuit open. I checked the wiring above the charcoal canister and sure enough the yellow wire was corroded right inside a black wire connector that connected 3 yellow wires together. Before i fixed it I would erase the code and the check engine light would come back on right after I started the car. After I respliced the wires together and erased the code the check engine light didn't come back on after I started it. Thanks a lot for the very helpful pictures and info!

A P0447 popped up the other day on my 2002 WRX but then went away. Unfortunately it's back. So, I'm going to try your solutions this weekend. Are the photos you mentioned available somewhere? I did not see them on the post.

The pictures are good but I can't tell if this canister is the same as the one on my 2005 RS. I'm getting the P0447 CEL and pretty sure it's because the 2-pinned connector is corroded. I need to replace the connector on the canister end and was able to remove it - it's actually a significant part about 3" long and one and half inches in diameter. It has a small o-ring at the outside end and a large o-ring near the other end. Subaru parts rep tells me that canister parts are not available separately. Can anyone identify this part? Photos available but I'm new to the forum and can't see how to upload.

Great write up. Got under my car and this is what it looked like. Wire was severed right at the connector.

In this case do I have to buy a new connector? Where can I source one from?

I've just found the same problem on my 05 RS. Corroded wire broke off right at the end of the plug. It would be a simple fix if I had a new connector. There's no Subaru dealer within 150 miles. Does anyone know of an online source for such things? I can find all sorts of sources for new evap canisters, but nothing for wiring harness plugs.

One of the pins is gone, completely corroded. But I found that the connector is attached to a part so I shouldn't have to replace the entire canister. Can anyone identify this part:
Connector on outside of canister:
This is the part removed from the canister with the connector on the right:
Other side view:
Top view of part:
View of metal pointed end on part:

I just made a direct connection to the pins where the plugs plugged into and taped it up like hell. Was not fun at all

The dealer confirmed that the plug isn't available. I cut off the plastic tube surrounding the pins and soldered on a wire to each pin. I then hooked the wires to the harness with a weather pack connector, and buried the soldered pins in silicon RTV gasket material to make them weatherproof. Worked perfectly.

I am annoyed at Subaru 'though. The dealer acknowledged that this is a common failure, but no repair parts are available.

i had an issue myself with an evap code that plagued me, ended up being the
charcoal cannister. saw bit of charcoal throughout my vac system. cannot rememeber the code tho. regardless, i think this beast of a post right here is dead on and definitely was helpful when tracking some of my issues.
thanks

I had the same cel p0447 when I check under the car I found the wire corroded as you described. Need to repin the connector thanks. My connector was in pretty bad shape too, so I searched. I came up with this if it helps anybody, sure seems to be the correct connector. http://www.dataspares.com/connectors/2-way/c2s-110b.

Awesome tutorial! It looked like mine was only hanging on by the wire sleeve. The loom revealed only 2 wires for me to cut. I extended the wires, put everything back, and cleared the code. P0447 no more! Thanks for this post!